As a typical rotary baler is driven along a crop windrow and crop material is continuously picked up and loaded into the baling chamber of the machine, the situation frequently arises in which the baling chamber is not loaded uniformly from one axial end thereof to the opposite end thereof. This is due largely because of the relatively narrow width of windrows compared to the overall length of the baling chamber, and unless the operator skillfully weaves his way along the windrow, the center of the baling chamber will necessarily become more heavily loaded than its opposite ends. This results in a bale which may be highly dense and fat in the middle but less dense and smaller diameter at its opposite ends.